Join Date: Dec 2016
Location: The state where 4 out of 7 former Governors went to jail
Thanked 888 Times in 746 Posts
Feedback Score: 0 reviews
Like I said and showed in my previous post, the PCM controls elevated idle based off engine coolant temp and engine run time...doesn't rely on open/closed loop conditions...engine temp and run time. Closed loop fueling on these cars start at surprisingly cool temperatures when ECT is ~5F and the rear O2s are at 50F.
One thing that could be the cause for long high idle is a thermostat that is stuck open, but that would usually lead to a DTC, very common when guys in the northern states swap the thermostat to 180F instead of the stock 203F.
Other than that, like I said and have seen with other M6 5.7s, the intake manifold bolts could be loose and grabbing false air. What is surprising with these motors is that if you pull the evap purge hose the engine will not throw a DTC but will adjust rpms through throttle/spark to compensate for the increased flow. Not sure how the 2015-2016 hell cats handle this as they also run a MAF, but all the other HEMIs don't seem to be terribly sensitive to vacuum leaks. On my 2013 JGC I noticed the idle was kind of funky, only to find the evap purge hose completely crack off at the throttle body. No DTC showed up and I only looked into the problem because the idle seemed rough when the engine was hot.